抄録
High pollutant concentrations, exceeding the Japanese environmental standard, have been observed in large cities during the winter night-time. One reason for this is the occurrence of a special meteorological condition, the nocturnal urban boundary layer (UBL), over the cities. In this paper, the basic modeling method for urban area was proposed. In this model, the turbulent diffusion coefficient was modeled by the turbulent kinetic energy (k) and energy dissipation rate (ε). The most important improvement of this model is the special treatment of urban building density by using form drag concept. The calculation result for the idealized urban condition shows the typical UBL characteristics. For the validation of the model, an extensive field observation result of the UBL structure conducted during January 1983 in Shinjuku, Tokyo, was presented. In this observation, the meteorological parameters and pollutant concentrations were observed using specially designed kytoon-mounted turbulence sonde system. The observed characteristics of nocturnal UBL including the land breeze penetration shows the good agreement with the model results. The proposed model can be used for the planning of the urban area in order to decrease the high pollutant concentration.
